From: Douglas Gilbert <dgilbert@interlog.com>
Date: Sun, 14 Jan 2018 17:00:48 -0500
Subject: [PATCH] blk_rq_map_user_iov: fix error override
References: bsc#1077989
Git-commit: 69e0927b3774563c19b5fb32e91d75edc147fb62
Patch-mainline: v4.16-rc1

During stress tests by syzkaller on the sg driver the block layer
infrequently returns EINVAL. Closer inspection shows the block
layer was trying to return ENOMEM (which is much more
understandable) but for some reason overroad that useful error.

Patch below does not show this (unchanged) line:
   ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
That 'ret' was being overridden when that function failed.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 block/blk-map.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 02c4e3a1befe..60e6e0629851 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -125,7 +125,7 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 	struct bio *bio = NULL;
 	struct iov_iter i;
-	int ret;
+	int ret = -EINVAL;
 
 	if (!iter_is_iovec(iter))
 		goto fail;
@@ -154,7 +154,7 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 	__blk_rq_unmap_user(bio);
 fail:
 	rq->bio = NULL;
-	return -EINVAL;
+	return ret;
 }
 EXPORT_SYMBOL(blk_rq_map_user_iov);
 
-- 
2.12.3